Heat dissipation of dynamic brakes



March 3E, 1953 E. J. JUsTUs 2,633,54

HEAT DISSIPATION oF DYNAMIC BRAKES Filed May 2L 194'? TANK lX- anu'll'wvt Z 9. 5 D

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fr T N e SWW/Wto@ l LU v EDGAR J JUSTA/S kD Patented Mar. 31, 1953 UNITED STATES PATENT OFFICE HEAT BISSIPATION F DYNAMIC BRAKES Edgar J. Justus, Atlanta, Ga.

Application May 21, 1947, Serial No. 749,57

9 Claims.

jMy invention relates to dynamic braking and more particularly to a system and method for disposing of the energy created in dynamic brakmg.

Diesel-electric locomotives now in operation in mountain service use dynamic braking on long 'downhill grades. The electric traction motors are turned into generators and the electrical energy created by the motors is converted to heat energy in resistor units. One method of dissipating this heat energy is by cooling the re sisters with air blown over them by fans built into the resistor banks. This method is not satisfactory because it requires a large resistor bank and a large ian to dissipate the large amount of energy created. The resistor bank and fan require a large amount of space, which is at a premium in a locomotive. Also, they add a substantial amount or" weight to the locomotive.

Another method commonly used for dissipating the heat energy is to mount the resistors in the bank of radiators for the cooling liuid of the diesel engine which is the prime mover. rEhe resistors in such an arrangement are cooled by the air iiowing over the bank of radiators. This method is objectionable because the dynamic braking is used only when the engine is idling and the cooling fluid is not being heated by the engine. The cooling iiuid in the radiators is consequently cooled, by the iiow of air needed to cool the resistors, to avery low temperature. The fluid, in turn, cools the cylinder and cylinder head of the engine to a lovv temperature. That low temperature is undesirable because a wide variation in temperature contributes to cracking of the cylinder and the cylinder head.

The present invention concerns a novel metho'd of dissipating the heat created in resistors for absorbing the electrical energy generated in dynamic braking, which method avoids the objections to the prior methods described above.

' One object of my invention is to provide a system for dissipating the heat created by con- Iversionoi the electrical energy generated in dynamic braking to heat energy in apparatus which is relatively compact and lightv in weight.

j Another object is to provide a system and method for dissipating the electrical energy created'in dynamic braking which comprises converting the electrical energy into heat and transferring the heat to the liquidin the cooling ciring as heat added to the 'cooling fluid'iof' an un'- loaded internal combustion engine, thereby maintaining the engine at an elevated temperature.

Still another object of my invention is to provide a system for dissipating the energy created in dynamic braking as heat added to the cooling uid of an internal combustion engine which system includes, for cooling said fluid, a fan whose speed is automatically varied with the amount of energy to be dissipated.

A still further object of my invention is to provide a system for dissipating the energy created in dynamic braking as heat added to the cooling fluid of an internal combustion engine, which system includes means for circulating said fluid in proportion to the amount of energy to be dissipated.

A clear understanding of my invention may be had by reference to the accompanying drawing, in which the single iigure is a diagrammatic representation of the cooling fluid and electrical connections for the braking system.

In the drawing, a prime mover, such as an internal combustion engine, is indicated by the reference numeral I. This engine may, for example, be a diesel engine such as those used in diesel-electric locomotives and drives a generator 2 through a shaft 3. The generator creates electrical energy which, through electrical conduits 4 energizes the electrical traction motors 6 and thereby drives the locomotive.

When the locomotive is going downhill, gravity furnishes the motive power and only a very small relative current isrequired of the generator to excite the elds 5 of the traction motors. Accordingly, engine I is idling when the locomotive is on a down grade. At such time the motors 6 are used for braking and, in such use, develop a large amount of electrical energy. This energy is conducted from the motors through commutator brushes l and electrical conduits 8 to resistance coils in a resistor box 9, in which most of the electrical energy is converted into heat.

The engine I is cooled by a huid, such as water, circulated through its cylinder Wall jackets. In cooling the engine, the fluid absorbs heat and is pumped through pipe I0 from the engine by a main circulating pump II, which may be driven through a shaft I2 and suitable reduction gearing by engine I so that the speed of the pump is proportional to the speed of the engine. From the pump II, the fluid flows through a pipe I3, an auxiliary pump I4 and a pipe l5 to the resistor box 9.' The latter is illustrated only dia- "grammatically in the drawing but is constructed with separate passages for the uid and the resistance coils, so that the latter are insulated electrically from the fluid but are in heat exchange relationship therewith. When electric current is passing through the resistance coils, they become heated and their heat is carried oif by the fluid, which leaves the resistor box 9 through pipe IS conducting it to the radiator II.

The pump I4 is necessary because in braking when the engine is idling, there is insufficient circulation for maximum heat transfer. The pump I4 is driven through a shaft I8 by an electric motor is, which is connected by leads 20 across an appropriate number of coils in the resistor box il. It is apparent that the voltage impressed across leads 2t, and therefore the speed of motor I9 and pump I4, will be proportional to the load on the resistor box 9. Thus, the amount of cooling fluid circulated by the auxiliary pump' I will be proportional to the amount of heat to be dispersed from the resistor box 9. Both pumps I I and Ill, being centrifugal pumps, dov not oder any resistance to flow through them. Whichever pump is being driven does the circulating and the other is just a slight restriction in the piping.

In the radiator I'I, the iluid is cooled by air blown over-the radiator coils by a fan 2l, which is driven by an electric motor 22. The fan motor is driven by power from the generator when the locomotive is loaded and appropriate switches disconnect it from the generator and hook it to the resistors when the unit is in braking. Thus, use the same fan for cooling both in braking and in normal operation. The motor 22 is connected by leads 23 across an appropriate number of coils in the resistor box 9. It will be appreciated that, as in the case of the motor I9, the speed of the motor 22 and ofthe fan 2 I, when connected to the resistors for braking will be in proportion to the load on the resistor box 9. Accordingly, the weight of air blown over the radiator il by the fan 2| will vary directly with the amount of heat to be dissipated from the resistor box 9 and, through the cooling duid, from the radiator II.

After the fluid is cooled in the radiator II, it passes therefrom through the conduit 2d to the cylinder wall jacket of the engine I, Where it serves the function, when the engine is loaded, of removing the heat of combustion. When the engine is not loaded, but is instead idling, the

.fluid passes through the engine jacket without being heated. This is the instance when the locomotive. is ,going downhill and the dynamic braking is being used, so that there is a load on the .resistor box s and the fluid removes the heat created in the resistance coils.

AnV expansion tank, or surge tank, 25 may be vincluded in the system at a proper place to provide for variations in volume and pressure of the Vcooling uid.

, A further feature of my invention is illustrated in the louvres or shutters 26 on the radiator Il, in front of the fan 2i These shutters are preierably controlled automatically through the. duct A2l by the. thermostat 23, which is inserted Vin the fluid conduit 2. The function of the thermostat 8 and the shutters 25 is to maintain the temperature of the duid entering the engine I at a certain minimum and maximum to avoid a vwide variation in the temperature oi the cylinder walls and thus reduce the possibility of the cylinders becoming cracked. This is accomplished by the thermostat Z acting, when the temperature .of the cooling fluid becomes lowto close the shutters 26 and thereby to restrict or shut oir the flow of air from fan 2| over the radiator I'I. Conversely, when the temperature of the iiuid becomes high, the thermostat 28 acts to open the shutters 26 and thereby permit a greater now of air from the fan 2 I over the radiator I'I.

It will be readily seen that Irhave provided a practical and eicient system for disposing of the heat generated in dynamic braking requiring a minimum of apparatus. The apparatus used in this system is compact, requiring a minimum of space and adding a minimum of weight. The apparatus required in this system is smaller and of less weight than that of prior systems because the weight and size of resistors which are cooled by a. circulating liquid is much less than the weight and size of resistors which are cooled by air.

When the engine I is running at full load, approximately as much heat is given off to the cooling fluid and through it to the radiator I'I as goes into useful work in the traction motors. Accordingly, the radiator il has a capacity for heat dissipation which is about equal to the brake horsepower of the engine. When the engine I is idling, and the traction motors I5 are used in dynamic braking, the maximum load on the motors is roughly equal to the maximum brake horsepower of the engine I. Therefore, the maximum amount of heat created in the resistor box 9 and to be dissipated in the radiator I is approximately equal to the capacity of the radiator, so that the radiator can adequately dissipate the heat of braking.

Becauseheat is added to the cooling uid in the resistor box 9, the engine I is not cooled to too low a temperature during long downhill runs when the engine is idling. As explained hereinabove, the control of the shutters 25 by the thermostat 23 further aids in maintaining the temperature of the cooling iiuid at a certain minimum, so that damage to the engine from cracking of the cylinders is avoided.

It is to be understood that the system of my invention is not limited to use in locomotives, but has other applications. For example, it may be usedwith engine-electric mine hoists where the engine cooling system can be used to dissipate the energy generated in braking the lowering of heavy loads dynamically, instead of using a brake band or brake shoes.

It will be seen that my system provides for adecuate heat dissipation in braking' equal to the neat dissipation taking place at full load in traction without requiring addition to the normal radiator capacity or the addition of extra fans. This is made possible by the` novel idea of introducing the heat to the engine cooling system at a time when. it is otherwise idle.

l' claim:

l. A dynamic braking system in which the electrical energy generated in braking is conyerted to heat in a resistor and said heat is absorbed in the cooling circuit of an internal com.- bustion engine, said cooling circuit including a heat exchanger and a fan for circulating air over said heat exchanger, said fan being driven by a motor energized from said resistor, whereby the speed of said motor and of said fan varies with the load on said resistor.

2. A dynamic braking system for use in connection with an internal combustion engine-electric traction motor drive having a cooling fluid circulating system, comprising a resistor for expending the power developed by said traction motor in braking and an auxiliary pump for circulating said cooling fluid through said resistor, said pump being driven by a motor energized from said resistor, whereby the speed of said motor and of said pump varies with the load on said resistor.

3. In a dynamic braking system in which a cooling fluid is circulated between a heat exchanger and the engine to cool the engine, the improvement comprising a resistor to convert the electrical energy generated in the braking system to heat, and a pump directing cooling fluid from the engine in heat transfer relationship with the resistors, said pump being driven by a motor energized by the resistors, whereby the rate of circulation of the cooling fluid is determined by the load on the resistors.

4. In a dynamic braking system in which a cooling fluid is circulated between a heat exchanger and the engine to cool the engine, the improvement comprising a resistor to convert the electrical energy generated in the braking system to heat, means to direct the cooling fluid from the engine in heat transfer relation with the resistors and to the heat exchanger, and a fan passing air over the heat exchanger for removal of heat therefrom, said fan being driven by a motor energized by the resistors whereby the rate of circulation of air over the heat exchanger is determined by the load on the resistors.

5. In a dynamic braking system in which a cooling fluid is circulated between a heat exchanger and the engine to cool the engine, the improvement comprising a resistor to convert the electrical energy generated in the braking system to heat, a pump directing cooling fluid from the engine in heat transfer relationship with the resistors, said pump being driven by a motor energized by the resistors, whereby the rate of circulation of the cooling fluid is determined by the load on the resistors, and a fan passing air over the heat exchanger for removal of heat therefrom, said fan being driven by a motor energized by the resistors whereby the rate of circulation of air over the heat exchanger is determined by the load on the resistors.

6. A dynamic braking system for an internal combustion engine-electric motor drive comprising a cooling system for the internal combustion engine including a heat exchanger and means for circulating a cooling fluid between the engine and the heat exchanger, a resistor electrical- 1y connected to the electric motor and heated by electrical current generated by the motor as the motor serves as a brake, means directing the cooling fluid of the cooling system in heat conducting contact with the resistors to extract the heat generated in the dynamic braking therefrom and then to the heat exchanger of the cooling system as the cooling fluid is circulated therethrough, and means responsive to the heat generated by the resistors for controlling the rate of dissipation of heat whereby the rate of dissipation of heat is increased with the load on the resistors.

7. A dynamic braking system for an internal combustion engine-electric motor drive comprising a cooling system for the internal combustion engine including a heat exchanger and means for circulating a cooling fluid between the internal combustion engine and the heat exchanger, a resistor electrically connected to the electric motor and heated by electrical current generated by the motor as the motor serves as a brake, means directing the cooling fluid of the cooling system in heat conducting relationships with the resistor to extract heat therefrom and then to the heat exchanger of the cooling system as the cooling fluid is circulated, and means for controlling the amount of heat extracted from the cooling liquid in the heat exchanger to control the temperature of the cooling fluid leaving the heat exchanger'.

3. A dynamic braking system for an internal combustion engine-electric motor drive comprising a cooling system for the internal combustion engine including a heat exchanger and means for circulating a cooling fluid between the internal combustion engine and the heat exchanger, a resistor electrically connected to the electric motor and heated by electrical current generated by the motor as the motor serves as a brake, means directing the cooling iiuid of the cooling system in heat conducting relationships with the resistor to extract heat therefrom and then to the heat exchanger of the cooling system as the cooling fluid is circulated, and thermostatic actuated means to control the amount of heat removed from the cooling fluid, in the heat exchanger to control the temperature of the cooling iiuid circulated to the internal combustion engine.

9. A dynamic braking system for an internal combustion engine-electric motor drive comprising a cooling system for the internal combustion engine including a heat exchanger and means for circulating a cooling fluid between the engine and the heat exchanger, a resistor electrically connected to the electric motor and heated by electrical current generated by the motor as the motor serves as a brake, means directing the cooling iiuid of the cooling system in heat conducting contact vvith the resistors to extract the heat generated in the dynamic braking therefrom and then to the heat exchanger of the cooling system as the cooling fluid is circulated therethrough, an auxiliary pump for circulating the cooling iluid and an auxiliary motor energized by the electrical current generated when the electric motor serves as a brake adapted to drive the auxiliary pump.

EDGAR J. JUSTUS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 381,815 Ries Apr. 24, 1888 1,372,864 Cox Mar. 29, 1921 1,489,501 Miner, Jr. Apr. 8, 1924 1,493,773 Dorion May 13, 1924 1,948,910 Furgason Feb. 27, 1934 1,992,568 Connor Feb. 26, 1935 2,097,166 Stone Oct. 26, 1937 2,215,296 Ogden Sept. 17, 1940 2,276,807 Tritle et al Mar. '17, 1942 2,313,503 Baldwin Mar. 9, 1943 2,336,052 Anderson et al Dec. 7, 1943 2,339,185 Nettel Jan. 11, 1944 

